# Method and apparatus of a multi-code code division multiple access receiver having a shared accumulator circuits

A Multi-Code (MC) Code Division Multiple Access (CDMA) receiver receives N (where N.gtoreq.1) encoded signal channels over multiple air signal paths. The N signal channels are encoded using a properly chosen subset of Walsh codes based on a Walsh-Matrix, W.sup.M, where M is a power of two. In the disclosed MC-CDMA receiver, a timing correlator means recovers the timing and control signal for the N signal channels received over any particular signal path; a FWHT circuit together with a second correlator means decodes all of the N signal channels.

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## Claims

1. A multicode (MC) code division multiple access (CDMA) receiver comprising

- rake receiver means for receiving a MC-CDMA signal including N (where N>1) signal channels with linearly modulated data being spread using binary spreading code sequences of N.sub.c chips,
- wherein each of the binary spreading code sequences of N.sub.c chips includes a plurality of N subcode sequences, where N.ltoreq.N.sub.c and wherein the nth subcode sequence, n=1, 2,..., N, of each of the N signal channels are encoded using subcode sequence H.sub.n or its binary inverse H.sub.n.sup.',
- a first complex correlator means for tracking and acquiring timing information for a preselected channel of the MC-CDMA signal, and
- a second correlator means, including a FWHT means, and utilizing the acquired timing information and the N subcode sequences for simultaneously decoding the N signal channels by correlating the corresponding intervals of the received signal by the subcodes H.sub.1, H.sub.2, H.sub.3,..., H.sub.N, and using these outputs as inputs to the FWHT.

2. The MC-CDMA receiver of claim 1 wherein said second correlator means includes

- a) a Base-Walsh-Code despreader for producing N.sub.c signal samples per symbol,
- b) an accumulator for accumulating the N.sub.c signal samples outputted from the Walsh despreader, wherein the accumulator is reset for every N.sub.c /N input samples, to produce N complex intermediate results,
- c) means for storing the N complex intermediate results, and
- d) a complex FWHT circuit, with N.sub.c -N log.sub.2 N complex additions where N is<or=to N.sub.c and where N=M=2.sup.i and i is>or=to 1 for processing the stored N complex intermediate results to form N correlator outputs.

3. The MC-CDMA receiver of claim 1 wherein said second correlator means includes

- a) a Base-Walsh-Code despreader for producing N.sub.c signal samples per symbol,
- b) an accumulator for accumulating the N signal samples outputted from the Walsh despreader, wherein the accumulator is reset for every N.sub.c /N input samples, to produce N complex intermediate results,
- c) multiplier for multiplying each of the N complex intermediate results by a channel weighting factor signal to form N real intermediate results,
- d) means for storing the N real intermediate results, and
- e) a real FWHT circuit, with N.sub.c +N log.sub.2 N complex additions, where N is<or=to N.sub.c and where N+M+2.sup.i and i is>or to 1, for processing the stored N real intermediate results to form N correlator outputs.

4. The MC-CDMA receiver of claim 1 wherein said first correlator means operates in a coherent mode.

5. The MC-CDMA receiver of claim 1 wherein said first correlator means operates in a non-coherent mode.

6. The MC-CDMA receiver of claim 1 wherein at least one of the N signal channels includes a Q and an I signal channels and the second correlator means decodes the Q and I signal channels.

7. The MC-CDMA receiver of claim 6 wherein the Q and I signal channels carry independent data signals.

8. The MC-CDMA receiver of claim 6 wherein the Q and I signal channels are combined to form a single data signal.

9. The MC-CDMA receiver of claim 1 being part of a user station of a MC-CDMA system including at least one base station and a plurality of user stations.

10. The MC-CDMA receiver of claim 1 being part of a base station of a MC-CDMA system including at least one base station and a plurality of user stations.

11. The MC-CDMA receiver of claim 1 wherein the spreading codes are orthogonal Walsh codes.

12. The MC-CDMA receiver of claim 1 wherein the binary spreading codes ate Walsh codes based on a Walsh-Matrix, W.sup.M, where M is a power of two.

13. The MC-CDMA receiver of claim 1 wherein the second correlator means includes a FWHT means, and includes at least N.sub.c +N/2 log.sub.2 N complex additions, and utilizes the acquired timing information and the N subcode sequences for simultaneously decoding the N signal channels bv correlating the corresponding intervals of the received signal by the subcodes H.sub.1, H.sub.2, H.sub.3,..., H.sub.N, and using these outputs as inputs to the FWHT.

14. The MC-CMDA receiver of claim 1 further comprising a common logic circuit for time-sharing an accumulator among said first and second correlator means.

15. A multicode (MC) code division multiple access (CDMA) receiver comprising

- rake receiver means for receiving a MC-CDMA signal including N (where N>1) encoded signal channels, the N signal channels being encoded using Walsh codes based on a Walsh-Matrix, W.sup.M. where M is a power of two,
- a first complex correlator means for tracking and acquiring timing information for a preselected channel of the MC-CDMA signal,
- a second correlator means, utilizing the acquired timing information and including a FWHT means for decoding the N signal channels, and
- wherein said second correlator means includes N.sub.c +N/2 log.sub.2 N complex additions, where N is<or=to N.sub.c and where N.sub.c =M=2.sup.i and i is>or=to 1.

16. A multicode (MC) code division multiple access (CDMA) receiver comprising rake receiver means for receiving a MC-CDMA signal including N (where N>1) encoded signal channels, the N signal channels being encoded using Walsh codes based on a Walsh-Matrix, W.sup.M, where M is a power of two,

- first complex correlator means for tracking and acquiring timing information for a preselected channel of the MC-CDMA signal,
- a second correlator means, utilizing the acquired timing information and including a FWHT means for decoding the N signal channels, wherein the spreading codes are Walsh codes based on a Walsh-Matrix, W.sup.M, where M is a power of two, and
- a common logic circuit for time-sharing an accumulator, for accumulating the timing information and the N signal samples, among said first and second correlator means.

17. A method of operating a multicode (MC) code division multiple access (CDMA) receiver comprising the steps of:

- receiving a MC-CDMA signal including N (where N>1) encoded signal channels, the N signal channels being encoded using binary spreading codes of N.sub.c chips, where N.sub.c is an integer.gtoreq.N,
- wherein each of the binary spreading code sequences of N.sub.c chips includes a plurality of N subcode sequences, where the nth subcode sequence n=1, 2,..., N of each of the N signal channels are encoded using subcode sequence H.sub.n or its binary inverse H.sub.n.sup.',
- tracking and acquiring timing information for a preselected channel of the MC-CDMA signal, and
- utilizing the acquired timing information and the N subcode sequences for simultaneously decoding the N signal channels by correlating the corresponding intervals of the received signal by the subcodes H.sub.1, H.sub.2,H.sub.3,..., H.sub.N, and using these outputs as inputs to the FWHT.

18. A method of operating a multicode (MC) code division multiple access (CDMA) receiver comprising the steps of:

- receiving a MC-CDMA signal including N (where N>1) encoded signal channels, the N signal channels being encoded using Walsh codes based on a Walsh-Matrix, W.sup.M, where M is a power of two, and,
- tracking and acguiring timing information for a preselected channel of the MC-CDMA signal,
- utilizing the acquired timing information and decoding the N signal channels using at least N.sub.c +N/2 log.sub.2 N complex additions, where N is<or=to N.sub.c and where N.sub.c =M=2.sup.i and i is>or=to 1.

**Referenced Cited**

**Patent History**

**Patent number**: 5870378

**Type:**Grant

**Filed**: Aug 20, 1996

**Date of Patent**: Feb 9, 1999

**Assignee**: Lucent Technologies Inc. (Murray Hill, NJ)

**Inventors**: Howard C. Huang (Red Bank Township, Monmouth County, NJ), Chih-Lin I (Manalapan Township, Monmouth County, NJ), Stephan ten Brink (Holmdel Township, Monmouth County, NJ), Charles Albert Webb, III (Rumson Township, Monmouth County, NJ)

**Primary Examiner**: Benedict V. Safourek

**Assistant Examiner**: Ken Vanderpuye

**Application Number**: 8/700,262

**Classifications**

**Current U.S. Class**:

**Walsh Functions (370/209);**Combining Or Distributing Information Via Code Word Channels Using Multiple Access Techniques (e.g., Cdma) (370/342); 375/208

**International Classification**: H04J 13021; H04B 7216;